The goal of proposal is the development of new optical probes for controlling intracellular signaling pathways. Over the past 15 years we have made many optical probes which we call caged compounds that have been the widely of all such probes in the field of cell physiology. For example, the caged calcium probes we have developed have been used in hundreds of experiments by many laboratories studying the physiology of many cell types. More recently, the caged neurotransmitters developed under the aegis of this grant have had wide impact. For any technology to be truly transformative it must not only address a significant unmet need, but it must also really work, it must be practical. In order to translate our technological innovations into reality we take a multidisciplinary approach, combining synthetic organic chemistry and photochemistry, laser photophysics, and cellular physiology. An additional vital feature of our work is that we have forged long-term collaborative relationships with noted physiologists. These interactions have been vital the development of useful and important caged compounds as it is the biological problems that define the probes. In this proposal we seek to address an important gap in the area of optical chemical methods that are used for photochemical probing of intracellular signaling pathways, namely, the ability to accomplish simultaneous, multimodal optical control of parallel signaling processes. The majority, but not all, of the new probes will involve the control of intracellular calcium. The temporal and spatial scales of the effects of changes in calcium are extremely wide, so optical methods that address all these levels are useful in the study of many types of cellular physiology. For example, synaptic transmission uses fast, local changes in calcium, whereas calcium-regulated gene expression uses more sustained changes in cellular calcium. In cardiac myocytes, fast local changes in calcium are converted into global calcium release events, via calcium-induced calcium release, which catalyze contraction. Because calcium is so important, it often is the integration point of symbiotic signaling systems that subtlety regulates calcium itself or use calcium to modulate parallel signaling pathways that are controlled by calcium at some level. The overall goal of this proposal is to develop new photochemical tools that allow bidirectional optical control of these signaling pathways.